Mesenteric Ischemia

Acute Mesenteric Ischemia is a rare but life threatening condition, which occurs due to interruption of the blood supply to the small intestine leading to bowel infarction and bowel necrosis.

Hence considered as a surgical emergency.
 

Small intestine has a rich blood supply mainly from superior mesenteric artery and a small contribution from inferior mesenteric artery and coeliac artery.

Small intestine receives about 25% of the cardiac output, which is almost similar to that of the kidney.



Superior Mesenteric Artery And It’s Branches

Classification Of Mesenteric Ischaemia
  • Acute mesenteric ischaemia
    • Acute occlusion of superior mesenteric artery (65 – 70%)
      • Embolic (50%)
      • Thrombotic (20%)
    • Non occlusive mesenteric ischemia (15 – 20%)
    • Mesenteric vein thrombosis (5 – 10%)
  • Chronic mesenteric ischaemia
 
Incidence : 1 :  1000 hospital admissions

Early detection and prompt interventions increases the rate of success

Prognosis : Overall prognosis is poor


Pathophysiology / Viscous Cycle Of Mesenteric Ischemia

Pathophysiology / Viscous Cycle Of Mesenteric Ischemia



Acute Occlusion Of Superior Mesenteric Artery

This is the most common cause of small bowel ischemia

 
Causes 
  • Embolism
    • After an atrial fibrillation 
    • After an MI
    • Commonly affect middle colic artery
  • Thrombosis
    • Atherosclerosis
    • Affects the origin of SMA at the aorta 
    • Worse prognosis than embolism 
 
Clinical Presentation
  • Abdominal pain 
    • Sudden onset
    • Severe (Out of proportion of physical findings)
    • Non specific 
  • Nausea, vomiting, diarrhea  
  • Sweating
  • Late presentation
    • Bloody diarrhoea 
    • Abdominal distension 
    • Features of peritonitis 
      • Fever
      • Features of shock 
      • Rigid abdomen 
      • Rebound tenderness
  • May have a previous history of MI, AF, PVD
  • Metabolic acidosis 


Non Occlusive Mesenteric Ischemia

This results from systemic perfusion or in low flow states, which causes vasospasms / sympathetic vasoconstriction

Causes

  • Congestive cardiac failure
  • Hypovolemia
  • Sepsis
 
Clinical presentation

  • Similar to that of occlusion of SMA
 
Prognosis – Very poor
 
 
Mesenteric Vein Thrombosis
Commonly affects the superior mesenteric vein and rarely inferior mesenteric vein.
Interruption of the venous drainage can cause patchy necrosis and this can ultimately affect the arterial supply leading to bowel ischemia.

Causes

  • Idiopathic
  • Hypercoagulability 
    • Antithrombin III deficiency
    • Protein C deficiency
    • Protein S deficieny
  • OCP
  • Sepsis
  • Malignancy
  • Portal hypertension


Clinical presentation

  • Abdominal pain 
    • Non specific
    • Nausea
    • Abdominal distension   
  • More insidious than arterial compromise 
  • More pronounced symptoms begin to occur when it starts to interfere arterial supply or develop complications (Perforation of bowel)

Investigations Of Acute Mesenteric Ischemia

  • Haematological tests
    • Complete blood count – Neutrophilic leukocytosis
    • ABG – Metabolic acidosis, ischemia (Elevated lactic acid
    • Serum amylase, ALP – For exclusion of other diseases
  •  Imaging studies
    • Erect X-Ray abdomen 
      • Dilated bowel loops
      • Thumb printing sign – Suggestive of bowel oedema
      • Pneumatosis intestinalis
      • Gas in portal vein 
    • Doppler studies 
      • Reduced velocity in the mesenteric vessels 
    • CECT scan
      • SMA thrombosis
      • Bowel odemea
      • Pnematosis intestinalis
      • Gas in vessels (Mesenteric veins, portal vein)
    • Angiography – Gold standard
      • Diagnostic and therapeutic method
      • CT angiography
      • MR angiography
        • Filling defects
        • Stenosis, blockage  
        • Sausage sign – Non occlusive mesenteric ischaemia 
 






             Fig : Angiogram









Management Of Acute Mesenteric Ischemia

Management Of Mesentric Ischemia


Download PDF file from here.



Chronic Mesenteric Ischaemia

Also known as intestinal angina.

Causes

  • Atherosclerosis

Clinical Presentation

  • Postprandial abdominal pain 
  • Fear of eating
  • Weight loss

Investigations
  • Same as acute mesenteric ischaemia
 
Management
  • Only done in severe cases
  • Bypass surgery
  • Angioplasty 
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